Comparison of different material models to simulate 3-d breast deformations using finite element analysis.

Biomechanical breast modeling using finite element (FE) analysis to predict 3-D breast deformations is of interest for various biomedical applications. Currently no consensus of reliable magnitudes of mechanical breast tissue properties exists. We therefore applied 12 material properties proposed in the literature to FE simulation models derived from prone MRI breast datasets of 18 female volunteers. A gravity free starting position is computed with an iterative FE algorithm followed by the calculation of the upright position of the breast and then compared to the real breast geometry in standing position using corresponding 3-D surface scans to determine the accuracy of the simulation. Hyper-elastic constitutive models showed superior performance than linear elastic models which cannot exceed the linear Hookean domain. Within the group of applied hyper-elastic material models those proposed by Tanner et al. (Med Phys 33:1758-1769, 2006) and Rajagopal et al. (Acad Radiol 15:1425-1436, 2008) performed significantly (p < 0.01) better than other material models. The advantage of the method presented is its non-invasive character by combining 3-D volume and surface imaging with automated FE analysis. Thus, reliable biomechanical breast models based on the presented methods can be applied in future to derive patient-specific material parameter sets to improve a wide range of healthcare applications.

Small-animal PET imaging of amyloid-beta plaques with [11C]PiB and its multi-modal validation in an APP/PS1 mouse model of Alzheimer's disease.

In vivo imaging and quantification of amyloid-ß plaque (Aß) burden in small-animal models of Alzheimer's disease (AD) is a valuable tool for translational research such as developing specific imaging markers and monitoring new therapy approaches. Methodological constraints such as image resolution of positron emission tomography (PET) and lack of suitable AD models have limited the feasibility of PET in mice. In this study, we evaluated a feasible protocol for PET imaging of Aß in mouse brain with [(11)C]PiB and specific activities commonly used in human studies. In vivo mouse brain MRI for anatomical reference was acquired with a clinical 1.5 T system. A recently characterized APP/PS1 mouse was employed to measure Aß at different disease stages in homozygous and hemizygous animals. We performed multi-modal cross-validations for the PET results with ex vivo and in vitro methodologies, including regional brain biodistribution, multi-label digital autoradiography, protein quantification with ELISA, fluorescence microscopy, semi-automated histological quantification and radioligand binding assays. Specific [(11)C]PiB uptake in individual brain regions with Aß deposition was demonstrated and validated in all animals of the study cohort including homozygous AD animals as young as nine months. Corresponding to the extent of Aß pathology, old homozygous AD animals (21 months) showed the highest uptake followed by old hemizygous (23 months) and young homozygous mice (9 months). In all AD age groups the cerebellum was shown to be suitable as an intracerebral reference region. PET results were cross-validated and consistent with all applied ex vivo and in vitro methodologies. The results confirm that the experimental setup for non-invasive [(11)C]PiB imaging of Aß in the APP/PS1 mice provides a feasible, reproducible and robust protocol for small-animal Aß imaging. It allows longitudinal imaging studies with follow-up periods of approximately one and a half years and provides a foundation for translational Alzheimer neuroimaging in transgenic mice.

Comparison between breast volume measurement using 3D surface imaging and classical techniques.

Quantification of the complex breast region can be helpful in breast surgery, which is shaped by subjective influences. However, there is no generally recognized method for breast volume calculation. Three-dimensional (3D) body surface imaging represents a new alternative for breast volume computation. The aim of this work was to compare breast volume calculation with 3D scanning and three classic methods, focusing on relative advantages, disadvantages, and reproducibility. Repeated breast volume calculations of both breasts in six patients (n=12) were performed using a 3D laser scanner, nuclear magnetic resonance imaging (MRI), thermoplastic castings, and anthropomorphic measurements. Mean volumes (cc) and mean measurement deviations were calculated, and regression analyses were performed. MRI showed the highest measurement precision, with a mean deviation (expressed as a percentage of mean breast volume) of 1.56+/-0.52% compared with 2.27+/-0.99% for the 3D scanner, 7.97+/-3.53% for thermoplastic castings, and 6.26+/-1.56% for the anthropomorphic measurements. Breast volume calculations using MRI showed the best agreement with 3D scanning measurement (r=0.990), followed by anthropomorphic measurement (r=0.947), and thermoplastic castings (r=0.727). Compared with three classical methods of breast volume calculation, 3D scanning provides acceptable accuracy for breast volume measurements, better spatial interpretation of the anatomical area to be operated on (due to lack of chest deformation), non-invasiveness, and good patient tolerance. After this preliminary study and further development, we believe that 3D body surface scanning could provide better preoperative planning and postoperative control in everyday clinical practice.

New aspects of breast volume measurement using 3-dimensional surface imaging.

Precise and objective calculation of breast volume is helpful to evaluate the aesthetic result of breast surgery, but traditional methods are unsatisfactory. Three-dimensional (3D) scanning of the body surface allows reproducible and objective assessment of the complex breast region but requires further investigation before clinical application. The main goal of this study was to investigate the precision and accuracy of breast volume measurement using 3D body scanning. Five independent observers standardized the 3D scanning method using 2 dummy models (n = 200) and examined its applicability with 6 test subjects and 10 clinical patients (n = 2220). Breast volume measurements obtained with the 3D-scanner technology were compared with reference measurements obtained from test subjects through nuclear magnetic resonance imaging. The mean deviation of the breast volume measurements of 1 test subject by all observers, expressed as percentage of volume, was 2.86 +/- 0.98, significantly higher than the deviation for the dummy models, 1.65 +/- 0.42 (P < 0.001). With respect to all clinical patients, the mean measurement precision obtained preoperatively was less precise than that obtained postoperatively (3.31 +/- 1.02 versus 1.66 +/- 0.49, respectively). Interobserver differences in measurement precision were not statistically significant. The mean breast volumes obtained by nuclear magnetic resonance imaging (441.42 +/- 137.05 mL) and 3D scanning (452.51 +/- 141.88 mL) significantly correlated (r = 0.995, P < 0.001). Breast volume measurement with 3D surface imaging represents a sufficiently precise and accurate method to guarantee objective and exact recording.